FIG. 1.

PsaA-, PspA-, PspC-, and PdB-specific plasma antibody responses during pneumococcal carriage. Groups of five BALB/c mice were intranasally challenged with ≈7.5 × 10⁶ CFU of Streptococcus pneumoniae EF3030 in 15 μl of Ringer's solution. Serum samples were collected 28 days postinfection, and S. pneumoniae PsaA-, PspA-, PspC-, and PdB-specific IgG subclass antibody levels in plasma were measured by ELISA, which was capable of detecting >20 pg/ml of IgG1, IgG2a, IgG2b, and IgG3 antibodies. The data presented are the mean antibody concentration ± standard error of the mean of three separate experiments with infected mice. Naïve mice displayed responses that were below the detection limit of the ELISA and are not shown. Asterisks indicate significant differences (P < 0.05) between the maximum and next highest antigen-specific IgG1, IgG2a, IgG2b, or IgG3 antibody level in infected mice.